These ready-made cylinders can be inserted in an arthroscopic procedure; they are often used after a sports injury. They are known as osteochondral scaffolds, because they support new bone and cartilage as it grows.

One such plug, TruFit CB, is approved for use with bone and cartilage injuries in Europe, Canada and Australia. Its maker is Smith & Nephew of Andover, Mass. It is sold in the United States under the name TruFit BGS, and is cleared for use to fill some voids or gaps in bone but not for cartilage repair. The TruFit plugs are being tried out by Dr. Riley J. Williams III, director of the Institute for Cartilage Repair at Hospital for Special Surgery in New York, where he treats many professional basketball and soccer players. Dr. Williams first used the devices to fill holes from which tissue had been taken for transplants, and, after seeing good results in MRII scans, experimented with using them for cartilage repair in about 250 patients. Doctors are permitted to use approved drugs and devices in unapproved, or “off label,” ways as they deem appropriate.

“I’m very pleased with the clinical results,” said Dr. Williams, who said he had no connection to Smith & Nephew. “It’s a less traumatic surgery and you are not damaging the other areas of the knee” by removing cartilage.